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glCopyTexSubImage2DEXT(3G)     OpenGL Reference	    glCopyTexSubImage2DEXT(3G)


NAME    [Toc]    [Back]

     glCopyTexSubImage2DEXT - copy pixels into a 2D texture subimage

C SPECIFICATION    [Toc]    [Back]

     void glCopyTexSubImage2DEXT( GLenum target,
				  GLint	level,
				  GLint	xoffset,
				  GLint	yoffset,
				  GLint	x,
				  GLint	y,
				  GLsizei width,
				  GLsizei height )

PARAMETERS    [Toc]    [Back]

     target   The target texture.  Must	be GL_TEXTURE_2D or
	      GL_DETAIL_TEXTURE_2D_SGIS.

     level    The level-of-detail number.  Level 0 is the base image level.
	      Level n is the nth mipmap	reduction image.

     xoffset  A	texel offset in	the x direction	within the texture array.

     yoffset  A	texel offset in	the y direction	within the texture array.

     x	      The x coordinate of the lower-left corner	of the pixel rectangle
	      to be transferred	to the texture array.

     y	      The y coordinate of the lower-left corner	of the pixel rectangle
	      to be transferred	to the texture array.

     width    The width	of the texture subimage.

     height   The height of the	texture	subimage.

DESCRIPTION    [Toc]    [Back]

     glCopyTexSubImage2DEXT replaces a rectangular portion of a	twodimensional
 texture image with pixels from	the current GL_READ_BUFFER
     (rather than from main memory, as is the case for glTexSubImage2DEXT).

     The screen-aligned	pixel rectangle	with lower-left	corner at (x, y)
     having width width	and height height replaces the portion of the texture
     array with	x indices xoffset through xoffset+width-1, inclusive, and y
     indices yoffset through yoffset+height-1, inclusive, at the mipmap	level
     specified by level.  (But see the paragraph about GL_INTERLACE_SGIX
     below).

     The pixels	in the rectangle are processed exactly as if glCopyPixels had
     been called, but the process stops	just before final conversion.  At this
     point all pixel component values are clamped to the range [0, 1] and then
     converted to the texture's	internal format	for storage in the texel



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glCopyTexSubImage2DEXT(3G)     OpenGL Reference	    glCopyTexSubImage2DEXT(3G)



     array.

     The destination rectangle in the texture array may	not include any	texels
     outside the texture array as it was originally specified.	It is not an
     error to specify a	subtexture with	zero width or height, but such a
     specification has no effect.

     If	any of the pixels within the specified rectangle of the	current
     GL_READ_BUFFER are	outside	the read window	associated with	the current
     rendering context,	then the values	obtained for those pixels are
     undefined.

     When GL_INTERLACE_READ_INGR is enabled, every other row of	the source
     pixel rectangle is	read.  The height of the source	pixel rectangle	is
     equivalent	to 2xheight.  Only rows	(y+0,y+2,...) of the source are	used
     to	define the rows	of the texture subimage	that are affected by the copy.

     When GL_INTERLACE_SGIX is enabled,	source pixels are written to every
     other row in the texture subimage,	rather than to every successive	row.
     The height	of the subimage	is equivalent to 2xheight.  Rows
     (yoffset+0,yoffset+2,...)	of the destination texture are affected, while
     rows (yoffset+1,yoffset+3,...) are	not modified.  A complete video	frame
     may be assembled in texture memory	by invoking glCopyTexSubImage2DEXT on
     two consecutive video fields, with	yoffset	values that differ by one.

NOTES    [Toc]    [Back]

     glCopyTexSubImage2DEXT is part of the EXT_copy_texture extension,
     GL_INTERLACE_SGIX is part of the SGIX_interlace extension,	and
     GL_INTERLACE_READ_INGR is part of the INGR_interlace_read extension.  See
     glIntro for more information about	using extensions.

ERRORS    [Toc]    [Back]

     GL_INVALID_ENUM is	generated when target is not one of the	allowable
     values.

     GL_INVALID_VALUE is generated if level is less than zero or greater than
     log (max),	where max is the returned value	of GL_MAX_TEXTURE_SIZE.
	2

     GL_INVALID_VALUE is generated if xoffset<-TEXTURE_BORDER,
     (xoffset+width)>(TEXTURE_WIDTH-TEXTURE_BORDER), yoffset<-TEXTURE_BORDER,
     or	(yoffset+interlacexheight)>(TEXTURE_HEIGHT-TEXTURE_BORDER).  Where
     TEXTURE_WIDTH, TEXTURE_HEIGHT, and	TEXTURE_BORDER are the state values of
     the texture image being modified, and interlace is	1 if GL_INTERLACE_SGIX
     is	disabled and 2 otherwise.  Note	that TEXTURE_WIDTH and TEXTURE_HEIGHT
     include twice the border width.

     GL_INVALID_VALUE is generated if width or height is negative.

     GL_INVALID_OPERATION is generated when the	texture	array has not been
     defined by	a previous glTexImage2D	(or equivalent)	operation.





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glCopyTexSubImage2DEXT(3G)     OpenGL Reference	    glCopyTexSubImage2DEXT(3G)



     GL_INVALID_OPERATION is generated if glCopyTexSubImage2DEXT is executed
     between the execution of glBegin and the corresponding execution of
     glEnd.

ASSOCIATED GETS    [Toc]    [Back]

     glGetTexImage


MACHINE	DEPENDENCIES
     RealityEngine, RealityEngine2, and	VTX systems do not support color
     matrix transformations on images as they are loaded to or read back from
     texture memory.

     RealityEngine, RealityEngine2, and	VTX systems support
     glCopyTexSubImage2D and glCopyTexSubImage2DEXT with the following
     restrictions:

	  1.  Only level 0 is supported; other levels result in	a
	      GL_INVALID_VALUE error.

	  2.  The texel	offsets	and the	dimensions of the subimage must	be
	      multiples	of 32; otherwise a GL_INVALID_VALUE error is
	      generated.

	  3.  If glCopyTexSubImage2D or	glCopyTexSubImage2DEXT is used when a
	      GLX video	source is the read drawable (see
	      glXMakeCurrentReadSGI), the X offset and Y offset	must both be 0
	      and the subimage width must be 768; otherwise a GL_INVALID_VALUE
	      error is generated.

	  4.  GL_INTERLACE_SGIX	is not supported (see glEnable).

     On	InfiniteReality	systems, there is a performance	benefit	when the width
     of	the image to be	transferred to texture memory is a multiple of 8.

     Texture borders are not supported on InfiniteReality systems.
     Applications should use borderless	textures and GL_CLAMP_TO_EDGE_SGIS
     wrap mode.

     On	High Impact and	Maximum	Impact systems,	if the right side of the image
     to	be transferred to texture memory is not	the right side of the texture,
     then its index must be a multiple of 32, where index = xoffset+width.
     Otherwise it will generate	a GL_INVALID_VALUE error.

     The SGIX_interlace	extension is supported only on InfiniteReality
     systems, on RealityEngine,	RealityEngine2,	and VTX	systems, on Octane2
     VPro systems, and on O2 systems.

     The INGR_interlace_read extension is supported only on Octane2 VPro
     systems, and on O2	systems.





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glCopyTexSubImage2DEXT(3G)     OpenGL Reference	    glCopyTexSubImage2DEXT(3G)



     On	O2 systems, when the current read drawable is a	DM pbuffer, using
     glCopyTexSubImage2D or glCopyTexSubImage2DEXT to copy into	a full texture
     image whose dimensions and	format match those of the pbuffer causes a
     copy-by-reference.	 This has performance advantages, especially for
     video-generated DMbuffers,	because	it provides a DMA path for updating
     textures.	Following the copy, rendering to the pbuffer or	otherwise
     modifying the DMbuffer, will directly affect texture memory.  However,
     this behavior is essentially an unspecified side-effect of	the
     implementation on O2, and cannot be used on other systems.

SEE ALSO    [Toc]    [Back]

      
      
     glTexImage2D, glTexSubImage2DEXT, glCopyPixels.


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